Well do you know when the original owner replaced the engine? The way you say: "...had an engine out of a newer model put in..." sounds like he put in an NBS (new body style, or 2004-2009 body) which would be odd because they have ETB and a harmonic balancer. If this is the case, you would search for that year engine.
BUT...I highly doubt this is the case. My 1998 4.2L went out in 2001-2002 so it has a 2001-2002 (Cant remember which year) engine in it, but that dosent matter because the design is the exact same as the 97's (sans the intake manifold). The Canada sticker you refer to is the engine assembly, as it is built in the Ford Essex plant in Canada. Could you possibly post a shot of the engine to be sure whether or not you have a NBS or OBS engine? But from a technical standpoint, I would believe it is an OBS engine so you would search for 1997 parts.
-Alex
P.S: It appears you are a new member in here, but for starters lets see some pics of the truck. Also, you might get more responses if you put this in the V6 forum.
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